1. Field of the Invention
The present invention relates to a vehicle tire having a tread pattern capable of improving wet performance and decreasing tire noise.
2. Description of the Related Art
Today, the noise originating directly from a vehicle is reduced. Therefore, tire noise contributes to the total noise level of the vehicle to a higher degree. Therefore, a substantial requirement now lies in reducing tire noise.
It is known that peak values of tire noise lie in a frequency range of 900 Hz to 1100 Hz. This noise is also termed organ pipe noise, because it is a consequence of the longitudinal grooves which become active in the contact patch of the tire. An air column is formed in the longitudinal grooves between the ground contact portion of the tire and the road surface, and this produces sound in the above-mentioned frequency range as a consequence of the resonance of the air column. The wavelength of the sound is substantially constant, independently of the speed, i.e. of the speed of rotation of the tire.
In addition, the tire noise further includes so-called pumping noise generated by a high speed flow of air in the axial grooves which also activates the longitudinal grooves, and so-called pitch noise which is generated by the tread pattern elements as a consequence of their circumferential pitch arrangement.
Because noise having a frequency of about 1000 Hz is easily perceived by the human ear, such noise disturbs people both inside and outside the vehicle. In order to reduce the generation of such noise, it would be possible to reduce the proportion of the negative tread pattern (i.e. to reduce the area of grooves), because a tire becomes quieter with a reduction of the negative tread pattern. However, wet performance such as aquaplaning becomes correspondingly worse with a reduction of the proportion of the negative tread pattern, since two oppositely directed effects are present, which have previously only enabled an unsatisfactory solution.